Shift-left testing: Difference between revisions

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{{Short description|Type of software testing}}

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'''Shift-left testing'''<ref>{{cite web|url=https://web.archive.org/web/20150905082941/https://insights.sei.cmu.edu/sei_blog/2015/03/four-types-of-shift-left-testing.html |title=Four Types of Shift Left Testing |author=Donald Firesmith | date=23 March 2015 |accessdatearchive-url=https://web.archive.org/web/20150905082941/https://insights.sei.cmu.edu/sei_blog/2015/03/four-types-of-shift-left-testing.html |access-date=27 March 2015|archive-date=2015-09-05 }}</ref> is an approach to [[software testing]] and [[system testing]] in which testing is performed earlier in the [[software development life cycle|lifecycle]] (i.e. moved left on the project timeline). It is the first half of the maxim "Testtest early and often.".<ref>{{cite web |url=https://msdn.microsoft.com/en-us/library/vstudio/ee330950%28v=vs.110%29.aspx |title=Test Early and Often |author=Microsoft | date=2012 |accessdateaccess-date=27 March 2015 |archive-date=2 April 2015 |archive-url=https://web.archive.org/web/20150402174955/https://msdn.microsoft.com/en-us/library/vstudio/ee330950(v=vs.110).aspx |url-status=live }}</ref> It was coined by Larry Smith in 2001.<ref>{{Cite journal|last=Smith|first=Larry|date=September 2001|title=Shift-Left Testing|url=https://www.drdobbs.com/shift-left-testing/184404768|journal=Dr. Dobb's Journal|volume=26|number=9|pages=56, 62|viaaccess-date=2020-06-04|archive-date=2020-06-21|archive-url=https://web.archive.org/web/20200621040103/https://www.drdobbs.com/shift-left-testing/184404768|url-status=live}}</ref><ref>{{Cite web|url=http://collaboration.cmc.ec.gc.ca/science/rpn/biblio/ddj/Website/articles/DDJ/2001/0109/0109e/0109e.htm|archive-url=https://web.archive.org/web/20140810171940/http://collaboration.cmc.ec.gc.ca/science/rpn/biblio/ddj/Website/articles/DDJ/2001/0109/0109e/0109e.htm|url-status=dead|archive-date=2014-08-10|title=Sep01: Shift-Left Testing|date=2014-08-10|access-date=2019-09-06}}</ref>

== Harm duebecause toof late testing ==

Shift-left testing is important because it helpsaims to prevent the following types of harm duecaused toby late testing:

* Testers may be less involved in initial planning, often resulting in insufficientInsufficient resources being allocated to testing.

* DefectsUndiscovered defects in requirements, architecture, and design, remainalong undiscovered whilewith significant effort is wasted while implementing them.

* Difficulty [[Debuggingdebugging]] (including identifying, localizing, fixing, and regression testing defects) becomes harder as more software is produced and integrated.

* Reduced [[code coverage]] during testing{{Citation needed|date=October 2017}} as a result of [[Encapsulation (object-oriented programming)|Encapsulationencapsulation]] impedesimpeding [[white-box testing]], reducing [[code coverage]] during testing.{{Citation needed|date=October 2017}}

* A “bow wave” of [[technical debt]] that can cause a project to fail.

* There is less time to fix defects found by testing, thereby increasing the likelihood that they will be postponed until later increments or versions of the system. This creates a “bow wave” of [[technical debt]] that can sink projects if it grows too large.

== Types of shift-left testing ==

There are four basic ways to shift testing earlier in the life-cycle (that is, leftward on the classic [[V-model]]). These can be referred to as traditional shift-left testing,<ref>{{cite web |url=http://www.velocitypartners.net/blog/2014/01/28/agile-testing-the-agile-test-automation-pyramid/ |title=Agile Testing - The Agile Test Automation Pyramid |author=Velocity Partners | date=28 January 2014 |accessdateaccess-date=27 March 2015 |archive-date=2 April 2015 |archive-url=https://web.archive.org/web/20150402164204/http://www.velocitypartners.net/blog/2014/01/28/agile-testing-the-agile-test-automation-pyramid/ |url-status=live }}</ref> incremental shift-left testing, Agile/DevOps shift-left testing,<ref>{{cite web |url=http://www.slideshare.net/Urbancode/shift-left |title=Shift Left: Approaches and Practices |author=Paul Bahrs | date=6 November 2014 |accessdateaccess-date=27 March 2015 |archive-date=6 April 2015 |archive-url=https://web.archive.org/web/20150406145122/http://www.slideshare.net/Urbancode/shift-left |url-status=live }}</ref><ref>{{cite web |url=https://www.ibm.com/developerworks/community/blogs/invisiblethread/entry/enabling_devops_success_with_shift_left_continuous_testing?lang=en |title=Enabling DevOps Success with Shift Left Continuous Testing |author=Dibbe Edwards |website=[[IBM]] |date=18 September 2014 |accessdateaccess-date=27 March 2015 |archive-date=2 April 2015 |archive-url=https://web.archive.org/web/20150402110506/https://www.ibm.com/developerworks/community/blogs/invisiblethread/entry/enabling_devops_success_with_shift_left_continuous_testing?lang=en |url-status=live }}</ref> and model-based shift-left testing.<ref>{{cite web |url=http://blog.sei.cmu.edu/post.cfm/using-v-models-testing-315 |title=Using V Models for Testing |author=Donald Firesmith | date=11 November 2013 |accessdateaccess-date=27 March 2015 |archive-date=2 April 2015 |archive-url=https://web.archive.org/web/20150402110448/http://blog.sei.cmu.edu/post.cfm/using-v-models-testing-315 |url-status=live }}</ref>

=== Traditional shift-left testing ===

As illustrated in the following figure, traditional shift-left moves the emphasis of testing lower down (and therefore slightly to the left) on the right hand side of the classic V model. Instead of emphasizing acceptance and system level testing (e.g., [[GUI testing]] with record and playback tools<ref>{{cite web |url=https://msdn.microsoft.com/en-us/library/dd286714.aspx |title=Record and Playback Manual Tests |author=Microsoft | date= 2013 |accessdateaccess-date=27 March 2015 |archive-date=2 April 2015 |archive-url=https://web.archive.org/web/20150402113241/https://msdn.microsoft.com/en-us/library/dd286714.aspx |url-status=live }}</ref>), traditional shift-left concentrates on [[unit testing]] and [[integration testing]] (e.g., using [[API testing]] and modern test tools). The transition to traditional shift-left testing has largely been completed.{{By whom|date=April 2016}}

<gallery>

Traditional-Shift-Left.jpg|Traditional shift-left testing

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=== Model-based shift-left testing ===

The previous forms all concentrated on testing earlier in the development cycle. However, they all test ''after'' software exists and seek to uncover only implementation defects. Model testing theory argues that 45% to 65% of defects are introduced before implementation, during requirements gathering, architecture, and design.<ref>{{cite webcn|url=http://www.iiste.org/Journals/index.php/CEIS/article/viewFile/3533/3581 |title=Quality Flaws: Issues and Challenges in Software Development |author1=P Mohan |author2=A Udaya Shankar |author3=K JayaSriDevi |name-list-style=amp | date=2012 |accessdate=27 MarchJanuary 20152021}}</ref>

Model-based testing moves testing to the left side of the Vs, by testing requirements, architecture, and design models. This shift begins testing almost immediately, instead of waiting a long time (traditional testing), medium time (incremental testing), or short time (Agile/DevOps) for software to become available to the right side of the Vs. This trend is just beginning.

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== References ==

{{reflist}}

== External links ==

* [https://devopedia.org/shift-left "Shift Left" Devopedia]

{{Software testing}}

[[Category:Software testing]]